Prepreg is an abbreviation of Preimpregnated Materials. It is a sheet-type product in which a matrix is ​​impregnated with reinforced fiber. The prepreg has very different properties depending on the orientation of the fibers and the weaving method, and the orientation of the fibers plays an important role in determining the mechanical strength of CFRP. Short and randomly oriented reinforcing fibers show isotropy, while long, unidirectional reinforcing fibers exhibit anisotropic behavior and are strongest when the applied load is parallel to the reinforcing fibers. Classification by the direction of the fiber is divided into unidirectional, orthogonal, multiaxial, and the like. Uni-directional refers to a state in which almost all fibers in the fabric are aligned in one direction. When the fibers used as reinforcing materials are aligned in one direction, the fibers are used in a straight line without twisting during the fabric production process, and there is an advantage in that the amount of fibers used as a whole can be minimized. A uni-directional prepreg exhibits different cutting forces depending on the stacking orientation angle. In this experiment, the optimal cutting conditions for a uni-directional prepreg 45 degree orientation angle specimen are presented.

Demand for CFRP with new characteristics is increasing in various industrial fields, from parts materials to daily necessities, and research on this is also being actively conducted. CFRP is a material that realizes properties suitable for multiple functions that cannot be seen in a single material by physically combining two or more materials with different shapes and chemical compositions. When machining CFRP using a high-speed steel (HSS) drill or a TiAlN-coating drill with different rotation speed and feed speed, the cutting force was experimentally analyzed and the optimal tool material and cutting conditions were selected. The cutting force according to the change in rotation speed of the high-speed steel drill and the TiAlN-coating drill is compared.

The emergency diesel generator of a nuclear power plant is a emergency AC power source that starts up within 10 seconds when a LOOP(Loss Of Off-site Power) occurs and supplies power to essential safety facilities. In this study, factors affecting start signal input time, engine rotation start time, 30% of engine rated speed, 80% of engine rated speed were studied to secure starting reliability. As a result, it was found that the section before the 30% of engine rated speed was affected by the mechanical management status from the start signal to the fuel oil linkage system. After the 30% of engine rated speed section, it was the maximum fuel supply section, and the time reduction effect through management improvement was insignificant.

Recently, car industry trend is downsizing, a lean-burn engine, green car and cost cutting. A turbocharger is the key components to improve fuel efficiency and power. This research is to study on the flow analysis in the performance analysis for change rotating speed of turbocharger turbine with three different rotating speed in the turbine. After measuring real design features, modeling, velocity distribution, pressure distribution and temperature distribution are conducted numerically. Torque and power are compared with three different cases in order to analyze the performance for turbine. Finally, optimum power is determined with the sequence of case 1, case 2, and case 3.

쌀은 우리나라 국민 식생활의 가장 중요한 곡물로써 생산량은 연간 420만톤에 이루고 있다. 그러나 쌀 소비량은 40 년 사이에 반으로 줄었다. 최근 국민 1인당 소비량은 2011년 71.2kg, 2013년 68.2kg, 2015년 62.9kg으로 매년 감소하고 있어 앞으로도 지속적으로 줄어들 것으로 예상된다. 또한 미처 소비되지 못한 쌀은 재고로 관리되고 있으며 이는 추 가비용을 발생시키고 있다. 쌀의 소비량 유지는 주곡의 안정적 생산 및 국가의 식량 안보를 유지하기 위해 반드시 지 켜야 할 과제이다. 서구화 된 식습관과 바쁜 생활환경 등으로 밥용의 쌀 소비 증가 또는 현행 유지는 현실적으로 어렵 다. 따라서 쌀 소비를 확대하기 위해는 이용의 다변화가 요구되는 시점이다. 현재 가공용 쌀 소비는 떡류 제조업에 29.7%, 주정 제조업 27.1%, 도시락 및 식사용 조리식품업 16.8%, 탁주 및 약주 제조업 8.1% 등 가공사업체에서 81.7%를 소비하 고 있다. 금후 쌀 소비를 확대하기 위해서는 쌀을 밀가루처럼 가공식품의 원료로 사용하는 방안이 필요하다. 그러기 위 해서는 우선 사용 용도에 맞는 저비용의 쌀가루 생산 기술이 필요하다. 현재 습식으로 분쇄하여 건조하는 쌀가루의 제 조비용은 500~700원/kg 수준으로 밀가루 300원/kg에 비해 2배 이상 들고 있다. 따라서 저비용 쌀 분쇄 기술 개발을 위 해 물에 불리지 않은 생쌀을 대상으로 수평회전 막대형 분쇄핀 방식의 핀밀을 사용하여 1차 시험을 하여 지난 해 학 술대회에서 발표하였으며, 이번 학술대회에는 시험요인을 확대하여 실험한 결과를 발표하고자 한다. 시험조건은 분쇄 장치의 배출체망 눈 크기 100~200mesh, 분쇄핀 회전수 2,900, 3,200, 3,500rpm이며, 원료 쌀 함수율은 13, 15, 17%로 하였다. 조사항목은 쌀가루의 함수율 변화 및 평균 입도 등이다. 시험결과 분쇄 쌀가루의 평균 입도는 회전수가 빠를 수록 분쇄가루(쌀가루 입도 범위 74.1~153.9μm) 입자가 고왔다. 함수율에서는 높을수록, 분쇄핀의 회전수가 빠를수록 분쇄가 잘되어 가루 입자크기가 작았게 나타났다. 이는 함수율이 높을수록 경도가 낮고 회전수가 빠를수록 쌀 입자에 가해지는 충격력이 크기 때문으로 생각된다. 이 시험결과를 토대로 현재 핀밀보다 고속으로 회전이 가능하고 충격력을 높일 수 있는 형태의 핀으로 개선제작 중에 있다. 시험후 결과를 분석하여 다음 학술대회에 보고할 계획이다.

Despite the importance of cycling postures during cycling performances, there has been a very little research investigating cycling postures and pedaling rate for particularly concerning domestic cyclists. The aim of this study was to analyze correlations and effects between cycling postures and pedaling rate in track cycling. Twelve male racing cyclists (six racing and university cyclists) participated in this research. For this study, seven infrared cameras (Qualisys ProReflex MCU-240s) were used for collecting data and these were processed via QTM (Qualisys Tracker Manager) software. It appeared that pedaling rate had correlations with regard to a shoulder angle (R=-.601) and displacement between shoulder joints(R= -.637), but a knee (R=-.601) and ankle angle (R=.667). Moreover, two multiple regression equations of pedaling rate for cycling postures were significant and R2 of the first order equation y (pedaling rate) = 0.039x (knee angle) - 1.068 was less than the second order equation y = 0.006x2 - 1.287x + 69.674. In conclusion, cycling postures affected the pedaling rate. Further study should be researched on postures in relation to air resistance in a wind tunnel.

The agitator with a reducer are usually using on the process of a water treatment. However, working the reducer at the field, a lubricant oil can leak out. It causes an environment pollution and a water service/sewerage pollution problem. In this study, the reducer with a drywell structure is developed in order to prevent the oil leakage. The drywell structure is that the reducer bottom housing and the support column of an output shaft are united, and taper roller bearings are in the bottom housing. During the development of the reducer, a mockup and a prototype are made by using CAD and a high speed CNC machine. Then, to prove the performance of the prototype, the performance tests, unload working test and the mechanical torque efficiency test, are conducted by the torque meter device. Also a motor velocity(rpm) control system is developed by a PID control according to the working loads(MLSS data). The results of the test are shown that the maximum torque efficiency is 88.45%, the oil leakage and the abnormal noise do not occur during the work. Therefore the reducer with the drywell structure and the motor rpm PID control system is successfully developed.